Optical chemical sensors based on sol-gel materials: Recent advances and critical issues

Abstract

Abstract. The use of the sol-gel process to produce materials for optical chemical sensors and biosensors is attracting considerable interest. This interest derives mainly from the design flexibility of the sol-gel process and the ease of fabrication. In most applications the sol-gel material is used to provide a microporous support matrix in which analyte-sensitive species are entrapped and into which smaller analyte molecules may diffuse. Sensors based on entrapped organic and inorganic dyes, enzymes and other biomolecules have been reported. A range of sensor configurations has been employed, including monoliths, thin films, as well as more elaborate structures. In this paper a selection is presented of recent significant developments in optical chemical sensors which employ solgel-derived materials. These developments include the tailoring of sol-gel materials to optimise sensor response, advanced waveguide structures and novel probe-tip sensors. Those issues which remain critical to the eventual deployment of sol-gel sensors are examined. In particular, the problems of leaching, microstructural stability, " diffusion-limited response time, and susceptibility to interferents are discussed and some solutions proposed.

Microcystin-LR detection in water by the Fabry–Pérot interferometer using an optical fibre coated with a sol–gel imprinted sensing membrane

“…It is a basic requirement of a chemical sensor to be able to maintain a fixed output over time when the sensor is exposed to a constant concentration of analyte (Mac-Craith et al, 1997). The perception of instability in interferometric readings with an OSA is not clear by the time of measure.…”

“…Sol-gel is a well-known process concerning transition of a system from liquid 'sol' (the colloidal suspension of particles) into solid 'gel' (Mac-Craith et al, 1997). The chemistry of sol-gel processes includes the hydrolysis of a precursor, condensation of the hydrolysis product to form a sol solution, gelatinizing the sol solution to form a gel, drying the formed gel and heat treatment of the dried sol-gel material (Dunn and Zink, 1991;Mujahid et al, 2010).…”

Cerâmicas bioativas: estado da arte

“…A imobilização de proteínas em vidros derivados desse méto-do apresenta grandes vantagens, tais como a de produzir materiais opticamente transparentes, ideais para desenvolvimento de sensores químicos e bioquímicos baseados em alterações de absorbância ou fluorescência. Como em biossensores os reconhecedores são componentes biológicos (enzima, anticorpo, antígeno), o processo bioquímico é a fonte do sinal analítico [46][47][48][49] . As vantagens potenciais da incorporação de biossensores à rede sol-gel são a alta sensitividade, o curto tempo de resposta, o pequeno tamanho e a facilidade de manipulação.…”

Sol-Gel Synthesis and Characterization of Lithium Yttrium Oxide

“…Sol-gel technique is simple and cheap, with good mixture of the reagents, low processing temperature and wide possibility to change the properties by varying the composition of the solutions [1,2]. The sol-gel process can be used to prepare thin films, fibers and powders, which finds wide applications in protective coating, superconductors, photocatalysis, glasses, dielectrics, ferroelectrics, electronics, sensors and insolating materials [1][2][3][4][5][6][7].…”